Gas turbine regenerator

ABSTRACT

A gas turbine regenerator for passing high pressure compressor discharge air in a heat exchange relation with hot turbine exhaust gases. An air inlet plenum and an air outlet plenum are disposed in a cross-flow relation with respect to the exhaust gas flow, within the exhaust gas flow, whereas a plurality of heat exchange unit pressure tubes fluidly interconnect said air plenums and are disposed in a generally parallel flow relation with respect to said exhaust gas, within the exhaust gas flow. Opposite ends of each unit pressure tube are received into either the air inlet plenum or the air outlet plenum whereby fluid communication between plenums is established and separation at each unit pressure tube opposite end is prevented. Thermal expansion of the heat exchange unit is substantially uniform since both the heat exchange pressure unit tubes and the air plenums are disposed within the hot gas flow.

1 United States Patent [1 1 Tramuta et al.

[ 1 Feb. 18,1975

[ GAS TURBINE REGENERATOR General Electric Company, Schenectady, NY.

22 Filed: Oct. 1,1973

21 Appl. No.: 402,261

[73] Assignee:

Primary ExaminerCharles J. Myhre Assistant Examiner-Theophil W. Streule,Jr. Attorney, Agent, or FirmErwin F. Berrier, Jr.

5 7 ABSTRACT A gas turbine regenerator for passing high pressurecompressor discharge air'in a heat exchange relation with hot turbineexhaust gases. An air inlet plenum and an air outlet plenum are disposedin across-flow relation with respect to the exhaust gas flow, within theexhaust gas flow, whereas a plurality of heat exchange unit pressuretubes fluidly interconnect said air ,plenums and are disposed in agenerally parallel flow relation with respect to said exhaust gas,within the exhaust gas flow. Opposite ends of each unit pressure tubeare received into either the air inlet plenum or the air outlet plenumwhereby fluid communication between plenums is established andseparation at each unit pressure tube opposite end is prevented, Thermalexpansion of the heat exchange unit is substantially uniform since boththe heat exchange pressure unit tubes and the air plenums are disposedwithin the hot gas flow.

3 Claims, 4 Drawing Figures PATENIED FEB18I975 3855,5711

SHEET 1 OF 2 GAS TURBINE REGENERATOR BACKGROUND OF THE INVENTION Thisinvention was made under contract with the United States Governmentunder Contract -35510 with the United States Maritime Administration ofthe Department of Commerce. The U.S. Government is licensed inaccordance with the terms of the aforesaid contract and has reserved therights set forth in Sections lfand 1 g of the Oct. 10, 1963 PresidentialStatement of Government Patent Policy.

The invention relates, in general, to heat exchangers; and, inparticular, this invention relates to gas turbine regenerators(recuperators). A regenerator (recuperator) is used in a gas turbinepower plant to heat compressor discharge air prior to its entry into thecombustion chambers thereby reducing the amount of fuel necessary tobring the combustion gases to the required operating temperatures. Heatis transferred to the compressor discharge air from hot turbine exhaustgases which pass through the regenerator in heat transfer relation withthe compressor discharge air. The regenerator includes alternating airand gas channels to effect the heat transfer.

Prior art gas turbine regenerators have included boxlike structureshaving plate-fin tube banks with the entire regenerator banded togetherby tie straps interconnecting massive structural end frames. Compressordischarge air, at relatively high pressure (about 130 psia) tends topush apart the tube banks as well as tending to warp or bow the endframe structure. In the prior art, bowing of the end frame structure wasprevented by using a plurality of relatively thick structural ribsincorporated into the massive end frame. The aforesaid construction isdisadvantageous in that a thermal mass mismatch is created between theend frames and tube banks in that the tube banks expand more quicklythan the end frames creating undesirable stressing in the regenerator.

An attempt to solve this problem is set forth in U.S. Pat. ApplicationSer. No. 383,705, for Tramuta et al.

filed July 30, 1973, and assigned to the assignee of the presentinvention. The application entitled Pressurized Strongback Regeneratorminimizes thermal mismatch by replacing the heavy structural ribs by apressurized air chamber at the ends of each tube bank.

It is therefore one object of the present invention to reduce theoverall weight of a gas turbine regenerator.

It is another object of the present invention to minimize thermalmismatch between the tube bundle and its support structure.

It is another object of the present invention to obviate massivestructural end frames and tie-straps in regenerator-construction.

Other objects and advantages will become apparent from the followingdescription of one embodiment of thepresent invention, and the novelfeatures will be particularly pointed out hereinafter in the claims.

BRIEF DESCRIPTION OF THE INVENTION According to the present invention, aregenerator may include one or several heat exchange modules, orsections each section comprising an air inlet plenum and an air outletplenum mounted in a cross-flow relation with respect to said exhaust gasflow. A heat exchange tube bank is positioned between the air inlet andoutlet plenums in a generally parallel flow relation to said exhaust gasflow, the tube bank including a number of unit pressure tubes. Each unittube includes an air passageway defined by a pair of spaced apartparallel plates attached together at their peripheral edges. There is aslotted opening at each opposite end of each pressure tube. Each airplenum -is formed with circumferential slots, along its axial lengthwhich receive therein respective opposite end unit pressure tube slottedopenings whereby the air inlet. and air outlet plenums are in fluidcommunication and opposite ends of each unit pressure tube are heldtogether by the slotted air plenums. Gas passageways are defined betweeneach pair of air passageways. The air inlet and outlet plenums are inthe hot gas flow and thus tend to expand uniformly with the heatexchange tube bank.

BRIEF DESCRIPTION OF THE DRAWINGS DETAILED DESCRIPTION OF THE INVENTIONA regenerative cycle for a gas t'urbine is well known and is, inparticular, shown in FIG. 1 of U.S. Pat. application Ser. No. 383,705,filed July 30, 1973, for Tramuta, Miller and Knox and assigned to theassignee of the present invention. Generally described, the regenerativecycle consists in passing compressor discharge air in a heat exchangerelation with hot turbine exhaust gases through a regenerator(recuperator) to raise the temperature of the air prior to thecombustion cycle. However, the present invention is applicable to anyheat exchange device and the present preferred embodiment isillustrative of one particular use.

Referring to the drawings of the present invention, FIG. 1 shows aregenerator 11 including an outer frame 13 of minimal construction andend flanges 15 for attaching the regenerator into an exhaust gas duct(not shown). The regenerator may be comprised of one or more heatexchange sections 17 each comprising a heat exchange tube bank 19 and anair inlet plenum 21 and an air outlet plenum 23. Flow arrows indicatethe exhaust gas flow direction and the compressor discharge air flowdirection. The air plenums are each formed with end flanges 25 forconnecting the air inlet plenum to the compressor discharge and the airoutlet plenum to the combustion chamber inlet respectively (not shown).

Each heat exchange section includes a heat exchange tube bank 19comprising a plurality of unit pressure tubes as shown in FIGS. 2, 3 and4. Each unit tube includes a pair of parallel, spaced apart plates 35aand 35b defining an air passageway 37 there between. Each air passagewaymay further include a number of staggered strip-fin means 39 interposedbetween the parallel plates providing alternating brazing surfaces S.The peripheral edges of each pair of parallel plates are joined toprovide a closed seam 4.3 forming a sealed perimeter about the unit tubeair passageway.

The unit pressure tube may be formed with a substantially rectangularsection including gas strip-fin means 49 on each air passageway outersurface. Moreover, the air passageways are extended beyond eachrectangular portion to form trapezoidal end portions each terminating inan open semi-circular slot.45 which permits air flow through the unittube air passageway. The gas strip-fin means may be attached to theouter surfaces of the rectangular section by brazing. Obviously, this isonly one of several possible configurations since the rectangularsection including gas strip-fin means may be extended to obviate thetrapezoidal end sections.

The air inlet and outlet plenums are formed with semi circular slottedopenings 55 which are disposed along the longitudinal axis of each airplenum. The slotted openings in the air inlet plenum are substantiallyaligned with and directed toward the slotted openings in the air outletplenum. Each unit pressure tube is disposed between the air plenums sothat the slot at one end is received into an air inlet plenum slottedopening and the slot at the opposite unit tube structure end is receivedinto an air outlet plenum slotted opening thereby fluidly communicatingthe air inlet plenum with the air outlet plenum through the plurality ofunit pressure tubes. Moreover, separation of the joined parallel platesis prevented at each end of the unit tube structureby the restraintimposed by the slotted pipes comprising the air inlet plenum and the airoutlet plenum respectively.

The operation of the regenerator is as follows. Hot turbine exhaust gasflows through the regenerator as indicated in FIG. 1. The air inletplenums and the air outlet plenums are disposed in a generallycross-flow relation with respect to the hot exhaust path as well aspositioned in the hot exhaust flow path. The plenums are interconnectedby heat exchange tube banks disposed in a parallel flow relation withrespect to the exhaust gas flow and positioned in the hot gas flow.Because. the plenums and heat exchange tube banks are both positioned inthe exhaust gas flow heating of component parts is more uniform.Moreover, the hotter air outlet plenum is positioned at the hot exhaustgas inlet, where the gas temperature is highest; whereas, the cooler airinlet plenum is positioned downstream, where the gas temperature iscooler, further contributing to more uniform heating and hence thermalexpansion.

The unique slotted plenum construction equalizes thermal mass byobviating massive end structures. The unit pressure tube, high pressure,air passageways are each held together by the slotted air plenum pipes,internal and peripheral brazing thereby providing a more uniformconstruction rather than relatively light heat exchange tube banks and amassive end structure associated with the prior art.

An additional advantage of the unit pressure tube construction isrealized in that individual tubes may be removed from the regeneratorfor maintenance and replacement.

While there is shown what is considered to be, at present, the preferredembodiment of the invention, it is, of course, understood that variousother modifications may be made therein; and, it is intended to cover inthe appended claims all such modifications as fall within the truespirit and scope of the invention.

What is claimed is: v

l. A heat exchange section for passing a high pressure air flow in aheat exchange relation with a high temperature gas flow comprising:

a tubular inlet and outlet plenum disposed in said housing, said tubularplenums having at least one open end for receiving and discharging saidhigh pressure air flow, a plurality of axially spaced, circumferentiallyelongated slots formed in said inlet and outlet plenums, said plenumsdisposed in spaced, generally parallel relationship with the slots ofone plenum generally facing and axially aligned with the slots of theother plenum; Y

a plurality of discrete high pressure air passage means for directinghigh pressure air flow from said inlet plenum to said outlet plenum andfor transferring heat thereto from said high temperature gas flowpassing through said housing, said means extending between andinterconnecting said inlet and outlet plenums and arranged in generallyspaced parallel relationship and in generally parallel flow relationshipto said gas flow with each said means comprising a pair of closelyspaced generally parallel plates joined together at their peripheraledges so as to define an air passageway therebetween and formed with anopen slot at opposite ends for flow into and out of said air passageway,each said passage means having one open end inserted into a slot of oneplenum and joined thereto and the other open end inserted into thecorresponding axial slot of the other plenum and joined thereto so as toform a gas passageway between each pair of high pressure passage means,whereby said passage means are connected to each other through andsupported exclusively by said tubular plenums so as to permit removaland replacement of an individual one of said passage means and to reducethermal stressing of said passage means.

2. The heat exchange section recited in claim l wherein the air inletplenum is downstream from the air outlet plenum with respect to said gasflow.

3. The heat exchange section recited in claim 1 wherein strip-fin meansare disposed between each pair of parallel plates having alternatingsurfaces in metal joined abutment to the interior surfaces of said unitpressure tube.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO.3,866,674 v DATED February 18, 1975 |NVENTOR(S) Salvatore S. Trqmutu etcrl It is certified that error appears in the above-identified patentand that said Letters Patent are hereby corrected as shown below:

In column 4, clcrim 1, insert the following line between lines 12 and13:

-- a housing;

Signed and Scaled this A ttest.

RUTH C. MASON C. MARSHALL DANN Arresting Officer (mnmissivnvr uj'Palenrsand Trademarks

1. A heat exchange section for passing a high pressure air flow in aheat exchange relation with a high temperature gas flow comprising: atubular inlet and outlet plenum disposed in said housing, said tubularplenums having at least one open end for receiving and discharging saidhigh pressure air flow, a plurality of axially spaced, circumferentiallyelongated slots formed in said inlet and outlet plenums, said plenumsdisposed in spaced, generally parallel relationship with the slots ofone plenum generally facing and axially aligned with the slots of theother plenum; a plurality of discrete high pressure air passage meansfor directing high pressure air flow from said inlet plenum to saidoutlet plenum and for transferring heat thereto from said hightemperature gas flow passing through said housing, said means extendingbetween and interconnecting said inlet and outlet plenums and arrangedin generally spaced parallel relationship and in generally parallel flowrelationship to said gas flow with each said means comprising a pair ofclosely spaced generally parallel plates joined together at theirperipheral edges so as to define an air passageway therebetween andformed with an open slot at opposite ends for flow into and out of saidair passageway, each said passage means having one open end insertedinto a slot of one plenum and joined thereto and the other open endinserted into the corresponding axial slot of the other plenum andjoined thereto so as to form a gas passageway between each pair of highpressure passage means, whereby said passage means are connected to eachother through and supported exclusively by said tubular plenums so as topermit removal and replacement of an individual one of said passagemeans and to reduce thermal stressing of said passage means.
 2. The heatexchange section recited in claim 1 wherein the air inlet plenum isdownstream from the air outlet plenum with respect to said gas flow. 3.The heat exchange section recited in claim 1 wherein strip-fin means aredisposed between each pair of parallel plates having alternatingsurfaces in metal joined abutment to the interior surfaces of said unitpressure tube.